1. Field of the Invention
This invention relates generally to the field of disk drives for mass information storage units for use in data processing systems, and more particularly to a new and improved housing for disks used in such drives.
2. Description of the Prior Art
Data processing systems typically include one or more mass data storage units in which data can be written on or retrieved from a magnetic medium. In modern data storage units, the magnetic medium typically may be deposited on and supported by an annular substrate such as aluminum. This disk is mounted in a drive in which it is rapidly rotated about its axis. The drive includes read/write heads which can be moved across the disk surface by an actuator in the drive to permit any one of a series of concentric annular data tracks to be accessed, the tracks being disposed on the substrate at differing radii. A drive may contain either a single disk or several disks stacked in spaced apart relation on a common spindle.
It has been an objective in recent years to increase the amount of data that can be stored on each disk, as well as the density at which the data is stored on the medium. This has necessitated an improvement not only in the magnetic medium itself, but also the techniques used in manufacturing the drive, as rigid mechanical tolerances must be maintained to ensure that the read/write heads maintain the proper spacings over the disks. A housing is typically provided to prevent attracting dust from the surrounding air. If dust is permitted to accumulate, the read/write head would have to fly farther from the disk, requiring the use of higher head flux densities and reducing the available storage densities. The dust on the surface would also cause excessive wear on the head and slider.
To increase the reliability of the high-density mass storage disk, the so-called "Winchester"-type disk drive was developed, in which the disks, the read/write heads and their actuating assemblies are all mounted in a housing assembly which is sealed to keep dust away from the disks. Filtered air may be directed over the annular disk surfaces to guard against the accumulation on the disks of any incidental dust which may seep into the housing. In prior art "Winchester"-type disk drives, as exemplified in U.S. Pat. No. 4,054,931 issued Oct. 18, 1977, the disk housing assembly comprises a metal base plate and a separate cover, of lightweight material such as plastic, which completes and seals the housing. A gasket may be used between the base and the cover to enhance the sealing. The base plate is usually larger than the cover, but the cover extends over the portion of the base plate necessary to enclose the disks and the head actuator.
The disk housing assembly is mounted in the disk drive cabinet, which includes a drive motor for rotating the disks, typically through a belt which cooperates with a disk spindle pulley projecting through the bottom of the housing. The drive also typically includes power supplies for driving the motor and drive control logic circuitry to facilitate reading and writing the data from and onto the disks.
The metal base plates of the prior art disk housings were susceptible to undesirable resonant vibrational modes which interfered with the heads accessing of the disks. To reduce these vibrations, heavy slab-like base plates were typically provided.
The size and weight of the base plate also served another purpose. In prior art disk housings the disk spindle, which supports and rotates the disks, is cantilevered on a duplex bearing mounted on the base plate. The rigid base plates provide the necessary support for the spindle against the vertical weight of the disks and the lateral pull of the drive belt as well as dynamic rigidity and adequate precision between the disk stack and the positioner, which contains the data and servo heads.
Furthermore, the larger weight of the prior art disk housings, typically weighing up to sixty pounds, required the cabinets containing the disk drives to be structurally enhanced to permit them to support the disk housings which added to the expense of the drives as a whole.
The invention disclosed herein provides a new and improved disk housing that is light in weight, low in manufacturing cost, and which provides the mechanical stiffness and structural rigidity needed for high density data storage and fast access time, without encountering objectionable resonances.